The present invention relates generally to soil test apparatus, and more particularly, is directed to an automatic hydraulic hammer which is compatible with and which can be employed in conjunction with existing hydraulic feed test boring drill machines.
In the construction industry, it is common practice to investigate underground soil and rock formations in order to properly evaluate site conditions in order to properly design foundations for structures such as buildings and roads. In conducting such investigations, various code officials and standard associations, such as the American Society for Testing and Materials have attempted to develop standard sampling procedures to establish reliable data concerning such engineering properties of soil as plasticity, permeability, unit weight, compressibility, strength and gradation. With respect to rock gathering data such as stratigraphy, lithology, structure and morphology has been found desirable. In the case of soils, the necessary information is usually determined by the Standard Penetration Test of Soils (STP) conducted in accordance with ASTM designation: D 1586-67 entitled "Standard Method For Penetration Test and Split-Barrel Sampling of Soils". In accordance with this standard, a drive weight assembly is specified which consists of a one hundred and forty pound weight, a driving head and a guide permitting a free fall of thirty inches. The lifting and dropping of the standard weight is usually accomplished by means of a winch which is part of a test boring drill machine.
Even though the standard penetration test is in general use and engineers have attempted to follow the criteria set forth in ASTM Standard D 1586-67, careful analysis of the results obtained have shown that the desired accuracy cannot always be guaranteed by using the presently employed methods due to such variables as inertia, friction of the winch, chattering of the weight along the guide rods as it drops and other inaccuracies inherent in the equipment.